What are the hidden dangers of the power lines of the tower crane in Guilin?


2021-03-24 09:22

1. In the three-phase four-wire system with direct neutral line, some people use repeated grounding to improve reliability; if a single grounding is used, when the metal structure of the tower crane leaks, the current passes through the grounding resistance of the tower crane and the neutral line. When the grounding resistance is returned to the power supply, since the resistance values ​​of the two grounding resistances are basically equal, their partial voltages are also basically equal, so that the grounding resistance of the tower crane has half the voltage of 220V. Since the current is not large, the voltage can exist for a long time. If a person stands on the wet ground and touches the leaking tower body, he should wait for the grounding resistance of the tower crane to withstand a similar voltage in parallel, so there may be a danger of electric shock. Guilin tower crane 2. Although the protective zero-connection measures can play a protective role, there are still potential safety hazards: in the three-phase four-wire system with the neutral line grounded, the tower crane adopts the protective measures of metal structure connecting to the working zero line. When the metal structure leaks, the leakage current returns directly to the zero line, forming a phase-to-zero short circuit. Due to the small resistance of the line and the large current, the fuse on the leakage line is quickly disconnected, which cuts off the leakage power supply and plays a protective role. . However, due to the current flowing through the working zero line when the electricity is unbalanced, and there is a certain resistance on the zero line, a certain voltage can be generated on the zero line, and a certain amount of voltage can be generated when the metal shell of the device is connected to zero. voltage, and at the same time pose a safety hazard.


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